Hard Inclusions Research Articles

Phase volume quantification of agarose-ghee gels using 3D confocal laser scanning microscopy and blending law analysis: A comparison

A thorough understanding of the phase behaviour of biomaterial composites is imperative for manipulating the structural and textural properties in novel food products. This study probed the phase behaviour of a model system comprising agarose and a varying concentration of ghee. Results obtained from scanning electron microscopy (SEM), micro differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and dynamic oscillation in-shear revealed discontinuous and hard inclusions of ghee reinforcing the continuous, weaker agarose matrix with increasing concentrations of the former. Phase behaviour of the system was quantified in parallel with a novel method combining 3D confocal laser scanning microscopy (CLSM) imaging and image analysis software - FIJI and Imaris - in an effort to substantiate the efficacy of the microscopic protocol in quantifying phase behaviour. Phase volumes recorded with the microscopic protocol were in close agreement to those modelled with the Lewis-Nielsen blending law using small-deformation dynamic oscillation. However, results indicated that the inner filtering effect or ‘self-shadowing’ observed commonly in CLSM images may pose a limitation to the application of this technique, necessitating further development before it can be applied to more complex, industrially relevant systems.

On the Effects of Constitutive Properties and Roughness of a Hard Inclusion in Soft Tissue on B-mode Images.

We perform finite element modeling of pulse-echo ultrasound of a hard inclusion in a soft tissue to gain a better understanding of B-mode image brightness characteristics. We simulate a pressure wave emitted by an ultrasound transducer through the inclusion-tissue medium by prescribing suitable boundary conditions, and collect the scattered wave response to simulate the behavior of the transducer array used for pulse-echo ultrasound. We form B-mode images from simulated channel data using standard delay and sum beamforming. We establish the accuracy of the finite element model by comparing the point spread function with that obtained from Field II ultrasound simulation program. We also demonstrate qualitative validation by comparing the brightness characteristics of rough and smooth surfaced circular inclusions with experimental images of a cylindrical metal tool immersed in a water tank. We next conduct simulation studies to evaluate changes in B-mode image brightness intensity and contrast related to different constitutive properties, namely, compressibility of the inclusion, impedance contrast between the host and inclusion, and surface roughness of the inclusion. We find that the intensity observed behind a hard inclusion in the axial direction is strongly affected by the compressibility and roughness of the inclusion. Also, the perceived width of the stone based on the intensity is greater for rougher stones. Our study indicates that imaging of compressible inclusions may benefit from targeted B-mode image forming algorithms. Our modeling framework can potentially be useful in differentiating hard inclusions from surrounding parenchyma, and for classifying kidney stones or gallstones.

C-Elastography: In Vitro Feasibility Phantom Study

C-Elastography (CE) is a new ultrasound technique that locally maps the non-linear elasticity of soft tissue using low-frequency (150–250 Hz) shear waves generated by the acoustic radiation force (ARF). CE is based on a recent finding that the magnitude of the ARF in an isotropic tissue-like solid is related linearly to a third-order modulus of elasticity, C, which is responsible for the coupling between deviatoric and volumetric constitutive behaviors. The main objective of the work described here was to examine the feasibility of using and performance of C-elastography in differentiating and characterizing soft tissue via a pilot study on ex vivo tissue and tissue-mimicking inclusions cast in a gelatin block. In this vein, the CE technique deploys a combination of ultrasound motion sensing and 3-D visco-elastodynamic simulation to estimate the non-linear modulus C. As ultrasound focusing inherently confines the ARF to a small region, CE provides the means for measuring C within O(mm3) volumes. Equipped with such data analysis, we performed in vitro CE experiments on agar-based, xenograft and normal breast tissue samples embedded in a gelatin matrix. The compound C-elastograms indicate marked (and sharp) C-contrast, with average values of 1.9 and 5.6 at push points inside the featured soft and hard inclusions, respectively.

Assessment of properties of coal seams as destructible environments

The article analyzes indexes that characterize properties of coal seams and are used in calculation of loads on cutting tools of mining machines, or in selection of drives. Determination of geological structure complexity of coal seams takes into account hard inclusions and dirt bands in coal, as well as their size and lithology type. The notion of coal cuttability in spalled and unspalled face zones is explained using the coefficient of coal spalling. For strength estimation of complex structure coal seams with dirt bands and hard inclusions, it is proposed to use the index of integral cuttability which is the sum of coal cuttability and generalized index of densities and properties of inhomogeneities in the seam. In geological documentation, strength characteristics of inhomogeneities are described using the ultimate compression strength or Protodyakonov factor of hardness (in Russia). For this reason, the authors propose an empirical expression to recalculate cuttability of inhomogeneities in terms of uniaxial compression strength or hardness factor. The estimation algorithms of brittleness, grindability and breakability of coal seams are presented. The formula of coal abrasiveness is given. Systematization of data on breakability of coal seams has made a framework for classification of coal seams as media disintegrated by cutting tools of mining machines.

Finite Element Study of Hard and Soft Inclusions in Hard/soft Matrix

Hard inclusions in the soft matrix are common in metal matrix composites. On the other hand, soft inclusions in the hard matrix can be found for instance in plastics like acrylonitrile-butadiene-styrene (ABS). This work focuses on the finite element study of hard inclusions in the soft matrix and soft inclusions in the hard matrix. Equivalent von-Mises Stress and Equivalent plastic strain are evaluated. Hard inclusions in the soft matrix produces higher plastic deformation than soft inclusions in the hard matrix but stresses are higher for soft inclusions in the hard matrix than for soft inclusions in the hard matrix along with plastic deformatio

Depth Estimation of Hard Inclusions in Soft Tissue by Autonomous Robotic Palpation Using Deep Recurrent Neural Network

Accurately detecting tumors and estimating the depth of tumors is essential in the surgical removal of tumors. In robotic-assisted surgery, autonomous robotic palpation has the potential to provide more precise detection, tumors’ depth estimation, and less intrusion when normal tissues surround tumors. In this article, by mimicking the human finger touch, we propose a tactile sensing-based deep recurrent neural network (DRNN) with long short-term memory (LSTM) architecture to improve the accuracy of the detection and depth estimation of tumors embedded in soft tissue. In the experimental setup, the hard inclusions simulate the tumors, while the phantom tissue is fabricated by silicon to simulate the soft tissue. During the experiment, the data from the force sensor and displacement of the robot palpation probe are for detection and depth estimation purposes. The collected sequential data set of the force and the displacement of the probe during one completed palpation process will go through the proposed DRNN network with deep LSTM architecture, in which the temporal dependencies of the sequential data will be captured in the cell states in the deep LSTM layers. Subsequently, the softmax classifier is adopted to determine if there is any hard inclusion exists and offer the depth estimation of the hard inclusions. Experiments based on 396 real data sets demonstrate that the detection accuracy for the testing data set is 99.2% and the depth estimation accuracy for the testing data set is 95.8%. The accuracy of the proposed method is best when comparing with other widely used methods. Note to Practitioners —The palpation of tumors motivated this article in the robot-assisted surgical systems through tactile feedback. In order to mimic the human touch on the soft tissue, this article presents a deep-learning-based approach to estimate the depth of the hard inclusions in the phantom tissue through force information. The displacement of the palpation probe and the touch force during one palpation are recorded as data sequences to train the deep model, which aims to capture dynamics and long-term dependence of the palpation process. In this article, we made the first successful attempt to accurately estimate the depth of the hard inclusions buried at different locations of the phantom tissue using only force information. The proposed approach can work in different robot-assisted scenarios, such as master–slave robotic surgery. In the clinic applications, the force sensor will be integrated at the end-effector of the robotic manipulator. According to the specific requirements, the force sensor and the robotic manipulator might be different from those used in this article. For some applications, such as the laparoscopic interventions, the complete vertical contact tends to be difficult to obtain due to the laparoscopic port effects. The projection of the recorded force data and displacement can obtain the information in the normal direction. The future work is going to be extended to tissue environments with arbitrary surface and tumors with various shapes/depths for more complex and prospective clinical applications.

Modeling of subsurface ceramic inclusions in metallic matrices

All engineering materials have the potential to contain inhomogeneities that can act as initiators for fatigue cracks during cyclic loading. One class of inhomogeneity that can occur as a result of the processes used to create metallic materials is a ceramic inclusion, typically resulting from the raw material contamination during the melting process. This article examines the predicted behavior of hard ceramic inclusions in a nickel-base superalloy metallic matrix. Compressive residual stresses are created in the inclusion during cool down from a stress-free state at high temperature. The influence of the proximity of the inclusion to the surface of the matrix material is examined, together with the impact of subsequent uniaxial loading on the stress field in the inclusion and in the surrounding material. The stress field in the ceramic inclusion is observed to transition from compressive to tensile as a function of the proximity of the inclusion to the surface of the material and the applied uniaxial stress field. For deep subsurface inclusions, the uniaxial stress field required to achieve a tensile stress in the inclusion is close to the yield stress of the material. The sensitivity of this critical stress to material cyclic hardening behavior and to the temperature difference between the stress-free state and the operating state is also explored. The significance of these modeling results is discussed in terms of the sensitivity of nickel-base superalloys to crack formation and growth from ceramic inclusions and hence the impact on probabilistic fatigue life assessments of the presence, location and size of the ceramic inclusions.

Evolutionary Algorithm Optimization of Staggered Biological or Biomimetic Composites Using the Random Fuse Model

In Nature, biological materials such as nacre, bone, and dentin display an enhanced mechanical strength due to their structure characterized by hard inclusions embedded in a soft matrix. This structure has inspired the design of artificial materials with optimized properties. Thus, for given the mechanical properties of matrix and inclusions, it is fundamental to understand how the global observables, essentially strength, and ultimate strain are determined by the geometrical parameters of the inclusions. In this paper, we address this question by extending the two-dimensional random fuse model, which has been widely used to extract statistical properties of fracture processes, to the case of staggered stiff inclusions. We thus investigate numerically how emergent mechanical properties can be optimized by tuning geometrical dimensions and the arrangement of the inclusions. To do this, we adopt an optimization procedure based on an evolutionary algorithm to efficiently explore the parameter space and to determine the most favorable geometrical features of the inclusions for improved strength or ductility, or both. Various lattice sizes and volume fractions are considered. Depending on inclusion sizes and aspect ratios, composite strength or ultimate strain can be maximized, with the Pareto front for simultaneous optimization of the two being interpolated by a simple power law. Characteristic exponents for damage avalanche distributions are found to vary with respect to homogeneous structures, indicating increased fracture ductility simply due to optimized geometrical features. Our study indicates the possibility through structural optimization of creating staggered composites that allow significant advantages in terms of weight reduction and fuel consumption in automotive applications.

Strain hardening behaviors and mechanisms of polyurethane under various strain rate loading

AbstractThe uniaxial tension experiments are performed on thermoplastic polyurethane to investigate its mechanical behaviors and related potential mechanisms, and the loading strain rate is designing to be wide ranging from 0.0001 to 1 s−1. It is found that the polyurethane presents an obvious rate‐dependence, and the stress strain curves share distinct strain hardening characteristics under the investigated strain rates. Furthermore, the strain hardening ratios are sharing nearly same trends and appear to be influenced by both strain rate and the induced adiabatic heating. Besides, the ratio is also strain‐dependent on previous loading history. Then, a two‐dimension unit cell model is built to investigate potential equivalent mechanisms, of which the hard phase as inclusion is equivalent with crystallization zone, crosslinking sites, and so forth. The simulation results facilitate to explain the distinct strain hardening ratios, even for the matrix from the extrapolated curves under super‐low strain rate loading. Finally, the analogic mechanisms of equivalent hard inclusions are proposed, which can reasonably explain the strain rate‐ and strain‐dependence characteristics of polyurethane mechanical behaviors.

Ultrasound Elasticity Imaging Based Multilevel Estimation Using Radiofrequency Data

An ultrasound elastography introduced to differentiate hard tumor inclusion embedded in soft tissue background based on similarity measurement of before and after deformation. In this study, freehand elastography has considered to localize hard inclusion embedded in soft tissue of phantom breast, where deformation generated by applying gentile compression using probe physical surface of ultrasound machine. Radiofrequency data of before and after deformation acquired and then processed off-line. A non-ability of refinement operation to regularize displacement estimation outliers at correlation window length of 2λ is addressed, where a multilevel processing algorithm has proposed to reinforce refinement operation by producing smooth elastography. In the first level of the processing, displacement field has estimated at correlation window length of 3λ, where global stretching as re-correlation operation and refinement operation as spatial regulation are included. While at second level, production of displacement estimation outliers at correlation window length of 2λ are regularized based on replacement of estimated cells with that interpolated one at first level. Results show an ability of multilevel algorithm to cope the issues that encountered previously proposed algorithm of refinement on estimation outlier free displacement field at an axial resolution of 2λ, and produces differential strain field.

Study on the effect of sample shapes on the thermal shock behavior of ZrB2‐SiC‐Graphite sharp leading edge

AbstractReliable evaluation of the thermal shock behavior of sharp leading edges (SLEs) was hampered by a lack of available experimental method in past decades. Herein, a novel water spraying method was utilized to investigate the shape effect of ZrB2‐SiC‐Graphite SLEs during thermal shock. Experimental results indicated that the critical failure temperature of ZrB2‐SiC‐Graphite SLEs was most sensitive to the wedge angle, which could lead to a dramatic attenuation by about 35% from 12° to 9°, and was relatively little affected by the tip radius of curvature and the thickness. Simulation results further revealed that the decay of critical failure temperature was mainly due to the significant stress concentration caused by the reduction of wedge angle. Scanning electron microscopy observation proved that cracks tend to bypass graphite flakes due to their weak interfacial bonding, while branching always occurred when encountering hard phases or inclusions.

Wear-Resistant Cast Iron Containing Spheroidal Graphite with a Two-Layer Ledeburitic–Martensitic Shell

The structure of a precipitation-hardened composite material, which consists of hard graphite inclusions coated with a two-layer ledeburite–martensite shell and uniformly distributed in a ductile metallic base, forms in the transition layer of high-strength spheroidal graphite cast iron chilled by surface quenching with melting. A process of volume heat treatment is proposed to form this structure in the volume of a product and to increase the abrasive wear resistance, the strength, and the impact toughness.

Fractured-Laminar Structure of Formations and Methods of Coal Loosening

The paper analyzes the structure of coal beds. It is noted that coal beds belong to laminar massifs with characteristic oriented structure and pronounced anisotropy of strength properties, and include rock layers and consolidated hard inclusions. The quality criteria of the coal loosening process are highlighted. A selective method of separating coal from a massif by cutting along weakened surfaces is proposed as an alternative to the existing combine technology with continuous cutting of a massif from the surface.

A modified yield function for modeling of the evolving yielding behavior and micro-mechanism in biaxial deformation of sheet metals

In-depth understanding of the evolving plastic yielding behaviors and insight into their micro-scaled mechanisms are critical for fully exploiting of the formability of sheet metals, accurately forming of the needed shape and geometries, and precisely tailoring of the needed quality and property of the deformed parts. In this research, the in-plane yielding behaviors of dual-phase steel and aluminum alloy sheets were extensively investigated by biaxial tension experiments with the original and pre-strained specimens. It is found that the profile of the experimental plastic work contours changes with the increase of plastic deformation, no matter what the proportional or complex loading condition is. This indicates that the evolving yield behavior cannot be neglected. Based on the Yld2000-2d yield function, a modified yield function with introducing a variable exponent to represent the evolving yield behavior was proposed and then employed to model the evolving yielding of the given metallic sheets. To investigate the yielding micro-mechanisms, the simulated biaxial tension tests were conducted by using the established representative volume elements (RVEs) with a crystal plasticity model. The simulation results showed that the texture of the given sheet metals has a significant effect on the profile of the yield loci. Moreover, when the hard secondary phase is added into the polycrystalline aggregate, the optimum exponent of yield function for the given RVEs is increased, instead of decrease within a certain range of the plastic strain. The micro-mechanism of the evolving yielding behavior could be attributed to the ‘pinning’ effect of hard inclusions to the polycrystalline grains, i.e. the hardly-deformable particles strengthening the kinetic constraints to the polycrystalline matrix and further obstructing the rotation and plastic deformation of the neighboring grains. This research thus provides a comprehensive understanding of the effect of microscopic structure (crystal structure, texture and secondary hard phase) on the macroscopic plastic yielding behavior of metallic materials as well as a new high-fidelity modelling technique to describe the evolving yielding behavior phenomenologically, in such a way to support the application of FE simulation in sheet metal forming processes.

Effect of superimposed compressive stresses on rolling contact fatigue initiation at hard and soft inclusions

A semi-analytical framework is introduced for the evaluation of favorable residual stresses for delaying rolling contact fatigue initiation. Subsurface stress histories are applied to a micro-scale model accounting for isolated inclusions of different types and geometries. Micro-scale von Mises stresses are calculated based on Eshelby’s method and considered as an estimator of crack initiation due to plastic deformation. The most critical cases in terms of micro-scale plasticity are identified, and the effect of macro-scale compressive residual stresses is considered. Finally, optimized residual stresses are determined that minimize the maximum attained micro-scale von Mises stress at different depths.

A proof of the Flaherty–Keller formula on the effective property of densely packed elastic composites

We prove in a mathematically rigorous way the asymptotic formula of Flaherty and Keller on the effective property of densely packed periodic elastic composites with hard inclusions. The proof is based on the primal–dual variational principle, where the upper bound is derived by using the Keller-type test functions and the lower bound by singular functions made of nuclei of strain. Singular functions are solutions of the Lame system and capture precisely singular behavior of the stress in the narrow region between two adjacent hard inclusions.

Theoretical Analysis of Simulating the Locked-In Stress in Rock Pore by Thermal Expansion of Hard Rubber

Rocks are composed of mineral particles and micropores between mineral which has a great influence on the mechanical properties of rocks. In this paper, based on the theory of locked-in stress developed by academician Chen Zongji, the locked-in stress problem in underground rock is simulated by the thermal expansion of hard rubber particles. The pore inclusion in rock is assumed to be uniformly distributed spherical cavities. Using the thermal stress theory, the stress of rock with a spherical pore inclusion is equivalent to the thermal stress generated by the spherical hard rubber inclusion. The elastic theory formula of the temperature increment and the equivalent pore pressure of the spherical hard rubber inclusion is derived. The numerical simulation of the rock mass model with a spherical hard rubber inclusion is carried out and compared to the theoretical calculation results; the results show that they are consistent. The method proposed by this paper for simulating stress distribution in rock by thermal stress is reasonable and feasible; it has a positive meaning for further study of mechanic phenomenon of rock with micropore inclusion.

Using a look-up table technique and finite element calculations for quick detection of stiff inclusions in silicone rubber

PurposeThe aim of the study was to show that a new method, using a look-up table technique, can be used to detect the presence and position of an inclusion embedded in a tissue-like material. Due to the time-consuming nature of the finite element (FE) method or FEM, real-time applications involving FEM as part of a control loop, are traditionally limited to slowly varying systems. By using a simplified two-dimensional FE model and a look-up table, we show by simulations and experiments that it is possible to achieve reasonable computational times in a tactile resonance sensor application.Design/methodology/approachA piezoelectric disk was placed in the center of a silicone rubber disk (SRD) with viscoelastic properties, where it acted as both sensor and actuator and dissipated radial acoustic waves into the silicone. The look-up table was constructed by calculating the radial Lamb wave transition frequencies in the impedance frequency response of the sensor while varying the position of an inclusion. A position-matching algorithm was developed that matched measured and calculated Lamb wave transitions and thereby identified the presence and position of an inclusion.FindingsIn an experiment, the position of a hard inclusion was determined by measuring the Lamb transition frequencies of the first radial resonance in two SRDs. The result of the matching algorithm for Disk 1 was that the matched position was less than 3% from the expected value. For Disk 2, the matching algorithm erroneously reported two false positions before reporting a position that was less than 5% from the expected value. An explanation for this discrepancy is presented. In a verifying experiment, the algorithm identified the condition with no inclusion present.Originality/valueThe approach outlined in this work, adds to the prospect of developing time-sensitive diagnostic instruments. This approach has the potential to provide a powerful technique to quickly present spatial information on detected tumors.

Selected Properties of Input Stock Material for the Production of Thin-Walled Cylindrical Products by Cold Flow Forming

This paper presents test results for the steel grade 15HGMV metallurgical purity, microstructure, method of production and effect on the mechanical performance of the input stock material for calibre 227 mm missile motor casings manufactured by cold flow forming. The reference product for the determination of preliminary design criteria of missile casings of the higher calibre were calibre 122 mm missiles manufactured in Poland. The final mechanical properties of the casings are a cumulative effect of quenching and tempering and strain hardening during cold flow forming. The research and industrial practice carried out so far have demonstrated that the production process of a Feniks missile (with a 1.5 mm thick casing wall) requires steel grades of extremely high purity. This steel grade is manufactured by VAD (Vacuum Arc Degassing) melting, followed by ESR (ElectroSlag Remelting) or, alternatively by melting and casting in vacuum oven. The content of hard and non-deformable non-metallic inclusions such as oxides is critical to the success of cold flow forming. The cal. 227 mm missile casings feature walls approximately 2.5 mm thick and produced by cold flow forming from a quenched and tempered intermediate product. New material specifications should be developed for this reason to enable correct cold flow forming and contribute to a significant improvement in the cost efficiency of manufacturing. The investigations covered herein were guided by an assumption that the thicker wall sections might make the material specifications applicable to lower-calibre missiles to restrictive and obsolete about cal. 227 missiles. After initial laboratory tests, this hypothesis will be verified in industrial experiments on the production of prototype missile casings from input stock materials varying in metallurgical purity.

Chromium effects on the microstructural, mechanical and thermal properties of a rapidly solidified eutectic Sn-Ag alloy

PurposeThis study aims to investigate the chromium (Cr) effects on the microstructural, mechanical and thermal properties of melt-spun Sn-3.5Ag alloy.Design/methodology/approachTernary melt-spun Sn-Ag-Cr alloys were investigated using X-ray diffractions, scanning electron microscope, dynamic resonance technique, instron machine, Vickers hardness tester and differential scanning calorimetry.FindingsThe results revealed that the Ag3Sn intermetallic compound (IMC) and ß-Sn have been refined because of the hard inclusions’ (Cr atoms) effects, causing lattice distortion increasing these alloys. The tensile results of Sn96.4-Ag3.5-Cr0.1 alloy showed an improvement in Young’s modulus more than 100 per cent (42.16 GPa), ultimate tensile strength (UTS) by 9.4 per cent (23.9 MPa), compared with the eutectic Sn-Ag alloy due to the high concentration of Ag3Sn and their uniform distribution. Shortage in the internal friction (Q−1) of about 54 per cent (45.1) and increase in Vickers hardness of about 7.4 per cent (142.1 MPa) were also noted. Hexagonal Ag3Sn formation led to low toughness values compared to the eutectic Sn-Ag alloy, which may have resulted from the mismatching among hexagonal Ag3Sn phase with orthorhombic Ag3Sn and ß-Sn phases. Mechanically, the values of Young’s modulus have been increased, with increasing chromium content, whereas the UTS and toughness values have been decreased. The opposite of this trend appeared in Sn95.8-Ag3.5-Cr0.7 alloy, which may have been due to high lattice distortion (ƹ = 16.5 × 10−4) compared to the other alloys. Increase in the melting temperature Tm, ΔH, Cp and ΔT was because of Ag3Sn IMC formation. The low toughness of Sn96-Ag3.5-Cr0.5 and Sn95.8-Ag3.5-Cr0.7 (109.56 J/m3 and 35.66 J/m3), relatively high melting temperature Tm (223.22°C and 222.65°C) and low thermal conductivity and thermal diffusivity (32.651 w.m−1.k−1 and 0.314 m2/s) make them undesirable in the soldering process. The high UTS, high E, high thermal conductivity and diffusivity, low creep rate and low electrical resistivity, which have occurred with “0.1 Wt.%” of Cr, make this alloy desirable and reliable for soldering applications and electronic assembly.Originality/valueThis study provides chromium effects on the structure of the eutectic Sn-Ag rapidly solidified by melt-spinning technique. In this paper, the authors compared the elastic modulus of the melt-spun compositions, which have been resulted from the Static method with that have been resulted from the Dynamic method. This paper presents new improvements in mechanical and thermal performance.